This invention relates to door hinges and, more particularly, to a continuous gear hinge that contains an intumescent seal.
The typical door is supported in a door frame with several hinges, each having two leaves provided with alternate knuckles that are held together with a hinge pin. Being manufactured from steel, these hinges can withstand the heat of a fire and indeed will continue to secure a door as long as the door and the frame in which it fits remain in place in the presence of the fire. But the typical knuckle-type hinge attaches a door to its frame in only a limited area, and while several are used on each door, the hinges remain vulnerable to abuse. It is not uncommon for the knuckle-type hinges on high-use doors, such as the doors one might find at the entrances to schools, to pull away from the edges of the doors or from the hinge jambs of their door frames. Resecuring the hinges with longer screws solves the problem temporarily, but often these screws eventually pull away from the doors or hinge jambs also.
Continuous or gear-type hinges provide a more practical solution to the problem of abuse. The leaves of this type of hinge have gear segments which mesh and also a cap which fits over and behind the gear segments to hold them together while allowing them to pivot relative to each other. The leaves may and often do correspond in length to the length of the door and door jamb and thus attach to the door and jamb at numerous locations, along the door edge and jamb. Hence, they do not easily pull away from either. But aluminum from which the leaves and cap are extruded melts at a relatively low temperature. In the event of a fire the exposed cap and gear segments of the gear hinge may melt, leaving the door unattached along its hinge jamb. A gust of wind or stream of water directed against the door could cause the door to fall out of its frame and enable the fire to propagate through and beyond the door frame. Even if the door remains in place, fire and smoke may pass through the gap left between the door edge and hinge jamb.
For this reason some gear hinges have stainless steel studs which, when the hinge is closed, project through the two leaves and into the hinge jamb and door to which the hinge is attached. In the event of a fire having enough intensity to melt the gear segments and cap, the studs remain in place and secure the door in the frame. But the hinge requires additional manual labor to accommodate the studs, and this adds to the cost of the hinge. Moreover, the studs complicate the installation of the hinge on a door and door frame and may even be removed or left off during installation.